Although the existence of a wide band, temperature stable, shear mode in X-cut lithium tantalate plates has been known for several years, attempts at constructing resonators operating in this mode, referred to as the fast shear mode, have been frustrated by the large number of spurious resonances occurring in the immediate vicinity due to other, unwanted modes. Most of these unwanted modes result, either directly or indirectly, from the excitation of the other planar shear mode, referred to as the slow shear mode, and from a series of flexural modes directly coupled to the fast shear mode.
Accordingly, it is the broad object of the present invention to suppress or eliminate the unwanted modes related to the slow shear mode.
It is a further object of the invention to position the flexural modes so as to place them outside the frequency band of interest.